Preventing alcohol and prescribed opioid/sedative misuse among military personnel including Reserve components, active duty soldiers, and Veterans is a national priority. The military is facing a crisis related to problematic alcohol and prescription drug use, particularly opioid and sedative misuse, and there is a critical need for effective prevention and early interventions. Service members with alcohol and/or opioid/sedative (AOS) misuse are at risk for poor outcomes such as injuries, reduced job performance, mental health problems, suicide, and HIV/other sexually transmitted infections. Although research in civilians indicates that Screening, Brief Intervention, and Referral to Treatment (SBIRT) approaches can reduce substance use and problems, these protocols have not been studied adequately in military personnel. This body of research also points to the need for strategies to reinforce gains in order to sustain Brief Intervention (BI) effects, but boosters to these interventions have not been well-studied. Emerging technologies, such as Web-based delivery of interventions and boosters provide the opportunity to tailor SBIRT interventions and address geographical barriers for military personnel such as the Army National Guard (NG). In addition, peer-outreach interventions have high levels of acceptability in military communities. The BuddytoBuddy peer support program, to be enhanced to include AOS misuse in this study, been used successfully in NG units. The proposed study will screen ~ 4,300 unique individuals over a 30-month enrollment period as part of Soldier Readiness Processing in the Michigan Army NG to identify 750 participants age 18-60 with alcohol and/or prescribed opioid or sedative misuse. Screenings via touch-screen computer tablets will be used to recruit NG members with alcohol/prescribed opioid or sedative misuse in the prior 3 months. Participants will be randomized to one of three conditions: 1) Web-delivered alcohol/prescribed drug misuse brief intervention with Web booster sessions (W+W; n=250); 2) Web-delivered brief intervention with Peer-delivered booster sessions (W+P; n=250); or 3) Enhanced Usual Care (EUC; n=250). The aims of the study are to develop, refine and test tailored motivational BIs with varied continuing booster reinforcements (Web vs. Peer) and to conduct a randomized controlled trial comparing the efficacy of these BIs (W+W; W+P) to usual care on subsequent alcohol/drug consumption and consequences, including injury, mental and physical-health functioning, and HIV risk behaviors at 4-, 8-, and 12-months post-enrollment. Random assignment will be stratified by gender and alcohol vs. prescription opioid/sedative misuse. The proposed study will directly inform leadership and key stakeholders about the impact of state-of-the-art technology-based BIs, combined with Web boosters or peer outreach, in NG military personnel to combat the growing scope of alcohol/prescription drug problems among U.S. reserve component and active duty soldiers. If successful, the results of the study will enhance translation to the general population and could have a major public health impact.